Choosing Your ISO Settings: What to Consider?

When you choose a particular ISO setting it affects both Aperture and Shutter speed, if you want a the perfect exposure. For instance, if you set the ISO higher, it will render a higher shutter speed or/and smaller aperture.

Ask yourself following queries while setting your ISO:

1. Light: How is the light provided for the shot? Is the subject well lit?
2. Grain: Do you want an image with noise/grain or not?
3. Tripod: Is a tripod or supporting equipment in your use? 
4. Subject Movement: Is your subject moving or still? 

The Above picture renders an image with changing ISO ratings and Shutter speed and Aperture kept constant. You can understand the various difference in the picture, other than grains.

If there is a lot of lights, you have no issue with some grain in the picture, you have a tripod or some equipment to stabilize your shots and the subject is still, then setting the ISO rating quite low will do your work.

On contrary, if your surrounding is dark, you want a grainy picture on purpose, your subject is in motion or you don't have a tripod, then increasing the ISO number will let you shoot with a fast shutter speed and well expose the shot too. 

Points to Remember:

High ISO: More Noise, Fast Shutter Speed, Small Aperture
Low ISO: Less Noise, Slow Shutter Speed, Large Aperture